1. Field of the Invention
The present invention relates to evaporation inhibitors, and to methods for using such inhibitors to reduce the evaporation of water from spray mixtures of agricultural chemicals.
2. Description of Related Art
Agricultural chemicals are widely used nowadays to safeguard the growth and yield of crops, and are usually applied by airplane to cover large areas under cultivation. To minimize the costs involved, every effort is made to keep the quantities of water required for diluting the commercial concentrates as small as possible and to apply high concentrations of active compounds in small amounts. Today, quantities of 5-50 liters/ha are applied by the low-volume (LV) method using known commercial products, such as wettable powders (WP), suspended concentrates (SC) or solvent-containing emulsifiable concentrates (EC) which are normally sprayed in suspension in 300-600 liters of water/ha using ground appliances.
The smaller the quantities of spray mixture applied per unit area, the finer the droplets applied have to be to obtain satisfactory coverage of the crops. This plus the high concentration of the spray mixtures has hitherto created the main obstacle to application of the low-volume method, particularly under sub-tropical and tropical climatic conditions, namely, the water evaporates too quickly due to the large surface area of the fine droplets, so that the active compound can readily be carried away by the wind. Losses are incurred through drifting and, depending on the plant protection agent used, may even cause damage to adjacent crops. Accordingly, exact dosage is difficult, particularly where the spray mixtures are applied from aircraft. Damage to the environment or losses of crop yield may have to be accepted.
In addition, heavy foaming can occur during preparation of the spray mixture with the greatly reduced quantities of water, because the dispersants and wetting agents in the wettable powders or concentrated dispersions are then present in correspondingly higher concentrations. The product foams out of the spray tanks unless the filling level is greatly reduced.
The above spray mixtures of agricultural chemicals are prepared from commercial concentrates by dispersion or emulsification in the desired quantity of water. The concentrates are either self-emulsifying solutions in an organic solvent (EC) or wettable powders (WP) or suspended concentrates (SC).
The agricultural chemicals used can be one or more of insecticides, fungicides, virucides, herbicides, acaricides, dessicants, growth regulators, ripening accelerators, repellents, pheromones, leaf fertilizers, defoliants, etc. In addition, the concentrates can optionally contain dispersants, emulsifiers, wetting agents, defoamers, stickers, carriers and pigments for obtaining a marking effect.
An object of the present invention is to reduce the evaporation of water in the low-volume method of applying agricultural chemicals in the form of spray mixtures. Measures in that direction are the subject of German Application No. 22 05 590, although the mineral-oil-based evaporation inhibitors claimed therein are not sufficiently effective under sub-tropical and tropical climatic conditions. In addition, it is known from U.S. Pat. No. 3,791,839 that the release of water from living plants, particularly during growth in dry climates, can be reduced by applying to the surface of the plants an aqueous emulsion which, in addition to paraffin wax and emulsifier, contains vaseline-like hydrocarbons (petrolatum) as an essential ingredient. However, the function of these emulsions is not to reduce the evaporation of spray mixtures of plant protection agents during spraying by the low-volume method.